My Windows installation has Latin and Cyrillic inputs enabled, but uses the English layout.

And I suddenly realized that non-unicode programs can not display Cyrillic symbols. They are displayed as ?.

So it seems that my codepage became broken or something... I believe it should be Windows-1251. But I don't know/remeber is there a global codepage settings? Maybe somewere in registry? I would prefer to not reinstall the OS.

Choose the Administrative tab, there is a section subtitled Language for non-unicode programs, click the Change System Locale … button.

The system locale determines the default character set (letters, symbols, and numbers) and font used to enter and display information in programs that don't use Unicode. This allows non-Unicode programs to run on your computer using the specified language. You might need to change the default system locale when you install additional display languages on your computer. Selecting a different language for the system locale doesn't affect the language in menus and dialog boxes for Windows or other programs that do use Unicode